Body fluid collection and analysis

ABSTRACT

The invention relates to attachable body fluid collection devices, each comprising at least one storage structure for, when in use, storing a body fluid sample secreted by a body fluid secreting surface. The or at least one of the storage structure comprises silicon. Particular emphasis is placed on sweat patches and techniques for analyzing sweat.

This application is the U.S. national phase of international applicationPCT/GB02/03731 filed 14 Aug. 2002 which designated the U.S. and claimsbenefit of GB 0120202.7, dated 18 Aug. 2001, the entire content of eachof which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

This invention relates to the collection of body fluids and to theanalysis of body fluids. More specifically this invention relates to thecollection of sweat and to the analysis of sweat.

The analysis of body fluids, of animals or humans, may be of value inthe detection of disease, or substances, such as drugs, absorbed by asubject. Blood, saliva, urine, and sweat have all been used for suchanalysis. Although blood is the most commonly tested fluid, sweatprobably provides the most inexpensive, safe, and convenient source of anumber of analytes. Devices used to collect sweat, are commonly referredto as sweat patches.

In addition to water and electrolytes, sweat contains trace elementssuch as zinc, cadmium and lead. The trace elements found in sweatprobably originate from blood serum. Labile metals can dissociate fromproteins under the influence of the concentration gradient existingacross blood capillaries, and diffuse through the capillary walls intothe sweat glands.

Other substances that have been identified in sweat include: ascorbicacid, thiamine, riboflavin, nicotinic acid, amino acids, ethanol,antipyrine, creatinine, thiourea, lactate, theophylline, parathion,tetrahydrocannabinol, and insulin. Examples of disease that have beenlinked to the increased presence of a particular chemical in sweatinclude: pronounced uremia, leukaemia, and diabetes.

Typically a patch is used to collect the substance of interest, from thesweat of a person being tested. The patch is adhered to the skin of theperson to be tested for a period of time, and sweat is absorbed into afibrous pad. The pad is then analyzed for the substance.

An example of a prior art sweat patch, generally indicated by 11, isshown in FIG. 1. In addition to the storage means which comprises afibrous pad 12, the patch comprises a semipermeable membrane 13 and abacking layer 14. The backing layer 14 is formed into a receptacle forthe fibrous pad 12 and has an adhesive surface 15 for bonding the patchto the skin 16 of the patient or person being tested. The semipermeablemembrane 13 separates the fibrous pad 12 from the dermal surface and maycontrol which, and the rate at which, analytes enter the receptacle.

The design of sweat patches is a complex process. It is desirable thatthe environment of the skin under analysis be as little affected aspossible by the presence of the patch. Sweating must occur or be made tooccur in order to test the sweat. For quantitative analysis, it isdesirable for the rate at which the analyte is collected to berelatively constant. The storage means used to collect the analyteshould have a composition and construction such that an appropriatetechnique may be deployed for separation and analysis of the sweatcontents. It is desirable that the storage means comprise a materialthat is reasonably stable when in contact with sweat.

The following documents each relate to part of the background to thepresent invention: U.S. Pat. No. 5,203,327; U.S. Pat. No. 4,756,314; GB2,303,847 A; GB 2,324,866 A; and JP 10080266 A.

A number of different devices are described in U.S. Pat. No. 5,203,327.The Main theme common to these devices is the presence of aconcentration zone that allows the concentration of a sweat component tobe increased for testing.

The main problem addressed by U.S. Pat. No. 4,756,314 is the largevariation in sweat uptake that may occur from individual to individual.The disclosure suggests that this variation may be reduced.

GB 2,303,847 A relates to bioactive silicon, resorbable silicon, andbiocompatible silicon.

GB 2,324,866 A relates to an analytical device for analyzing biologicalmaterials such as blood and bile.

JP 10,080,266 A this document discloses equipment for immobilisation ofa biopolymer or organism.

SUMMARY OF THE INVENTION

It is an objective of the present invention to address at least some ofthe above mentioned issues.

According to a first aspect, the invention provides an attachable bodyfluid collection device comprising at least one storage means for, whenin use, storing a body fluid sample secreted by a body fluid secretingsurface, characterised in that the or at least one of the storage meanscomprises silicon.

Preferably the silicon, from which the or at least one of the storagemeans is at least partly formed, comprises silicon that has beenpartially oxidized. More preferably the or at least one of the storagemeans comprises a storage sample of porous silicon, the sample of poroussilicon being partially oxidized.

For the avoidance of doubt the term “partially oxidized” is used, in thespecification, to describe a material that has been oxidized in such amanner that part of the material remains completely unoxidized.Therefore a sample of porous silicon that had been partially oxidizedwould comprise porous silicon in a completely unoxidized state.

Advantageously the silicon, from which the or at least one of thestorage means is at least partly formed, comprises silicon that has beenpartially oxidized in such a manner that a monatomic layer of silicon isformed on at least part of the surface of the silicon. Moreadvantageously the or at least one of the storage means comprises astorage sample of porous silicon, the sample of porous silicon beingpartially oxidized in such a manner that a monatomic layer of silicon isformed on at least part of the surface of the silicon.

The or at least one of the storage means comprises a storage sample ofporous silicon, the sample of porous silicon being partially oxidized insuch a manner that between 0.1% and 99% of the porous silicon atoms arebonded to oxygen. The or at least one of the storage means comprises astorage sample of porous silicon, the sample of porous silicon beingpartially oxidized in such a manner that between 0.1% and 10% of theporous silicon atoms are bonded to oxygen. The or at least one of thestorage means comprises a storage sample of porous silicon, the sampleof porous silicon being partially oxidized in such a manner that between0.1% and 50% of the porous silicon atoms are bonded to oxygen.

The or at least one of the storage means may comprise silicon oxide. Theor at least one of the storage means may comprise porous silicon oxide.

Advantageously the or at least one of the storage means comprises astorage sample of porous silicon that has been partially oxidized, thepartially oxidized porous silicon having a structure and compositionsuch that it is substantially un-corroded after contact with simulatedhuman sweat for a period between 5 minute and 1 year.

More advantageously the or at least one of the storage means comprises astorage sample of porous silicon that has been partially oxidized, thepartially oxidized porous silicon having a structure and compositionsuch that it is substantially un-corroded after contact with simulatedhuman sweat for a period between 5 minutes and 1 month.

Yet more advantageously the or at least one of the storage meanscomprises a storage sample of porous silicon that has been partiallyoxidized, the partially oxidized porous silicon having a structure andcomposition such that it is substantially un-corroded after contact withhuman sweat for a period between 10 minutes and 10 days.

Even more advantageously the or at least one of the storage meanscomprises a storage sample of porous silicon that has been partiallyoxidized, the partially oxidized porous silicon having a structure andcomposition such that it is substantially un-corroded after contact withhuman sweat for a period between 1 hour and 24 hours.

The or at least one of the storage means may comprise a siliconparticulate product, the silicon particulate product comprising amultiplicity of silicon particles, each silicon particle comprising oneor more of: bulk crystalline silicon, porous silicon, polycrystallinesilicon, and amorphous silicon. At least some of the silicon particlesmay be partially oxidized.

The mean particle size of the silicon particulate product may be between1 micron and 1 mm. The mean particle size of the silicon particulateproduct may be between 10 microns and 100 microns.

Once a sufficient quantity of the body fluid has been collected by theor at least one of the storage means, the sample of body fluid may beanalyzed by a suitable analytical technique. The analysis may beperformed in situ, or it may be performed after the collection iscomplete.

The collection device may further comprise an analytical means foranalyzing at least part of the body fluid sample.

Preferably the attachable body fluid collection device further comprisesan attachment means for attaching the or at least one of the storagemeans to part of a surface of an animal or human body. The attachmentmeans may comprise a tape or sheet or fabric or plastic material. Theattachment means may comprise an adhesive or flexible band or flexiblegarment. The garment may be designed to surround part of the animal orhuman body, for example the garment may be a glove or sleeve or cuff orhead band or wrist band or arm band. The attachment means may comprise asolid object. The attachment means may be a ring, or necklace, orbracelet.

The silicon, from which the or at least one of the storage means is atleast partly formed, may be selected from one or more of: poroussilicon, polycrystalline silicon, amorphous silicon, bulk crystallinesilicon, resorbable silicon, bioactive silicon, and biocompatiblesilicon.

For the purposes of this specification the term bioactive silicon is tobe taken as silicon that is capable of forming a bond with livingtissue. For the purposes of this specification the term resorbablesilicon is to be taken as a form of silicon that is corrodible in aphysiological liquid. For the purposes of this specification the termresorbable silicon is to be taken to include silicon that is resorbablein sweat. In other words the term resorbable silicon encompasses siliconthat corrodes in sweat.

Preferably the silicon, from which the or at least one of the storagemeans is at least partly formed, comprises a storage sample of poroussilicon. More preferably the storage sample of porous silicon has astructure such that the porous silicon is substantially un-corrodedafter contact with simulated human sweat for a period greater than orequal to 10 minutes. Yet more preferably the storage sample of poroussilicon has a structure such that the storage sample is substantiallyun-corroded after contact with simulated human sweat for a periodgreater than or equal to 20 hours. Even more preferably the storagesample of porous silicon has a structure such that the storage sample issubstantially un-corroded after contact with simulated human sweat for aperiod greater than or equal to 1 week.

Advantageously the storage sample of porous silicon has a porositybetween 1% and 99%, more advantageously the storage sample of poroussilicon has a porosity between 10% and 80%, even more advantageously thestorage sample of porous silicon has a porosity between 10% and 60%.

The storage sample of porous silicon may comprise microporous silicon,having a pore diameter between 1.0 and 2.0 nm.

The storage sample of porous silicon may comprise mesoporous silicon,having a pore diameter between 2.0 and 50 nm.

The storage sample of porous silicon may comprise macroporous silicon,having a pore diameter between 50 nm and 5 microns.

Simulated human sweat is herein defined as an aqueous solutioncomprising NaCl (20 g/litre), NH4Cl (17.5 g/litre), urea (5 g/litre),acetic acid (2.5 g/litre), and lactic acid (15 g/litre).

This definition corresponds to that of ISO standard (3160/2), which isdescribed by J P Randin in J Biomed Mater Res 22, 649 (1988).

The pH may be adjusted to 5.5 by the addition of NaOH.

The pH may be adjusted to 6.5 by the addition of NaOH.

The simulated human sweat may substantially consist of an aqueoussolution of NaCl (20 g/litre), NH4Cl (17.5 g/litre), urea (5 g/litre),acetic acid (2.5 g/litre), and lactic acid (15 g/litre) and NaOH, theconcentration of NaOH being such that the pH of the simulated humansweat is between 3.0 and 7.0.

The body fluid secreting surface may be an internal surface, found sayin the mouth of an animal or human, or an external surface, such as thesurface of skin of an animal or human.

The body fluid secreting surface may be skin, or a mucous membrane or abuccal membrane or a nipple. Preferably the body fluid is sweat, thebody fluid sample being a sweat sample. Advantageously the body fluidcollection device is a sweat patch.

The sweat sample may comprise a sweat element. The sweat sample maycomprise a sweat compound.

For the absence of doubt the term “body fluid sample” is to be taken asa sample of one or more substances that may be found in a body fluid ofan animal or human. Similarly the term “sweat sample” is to be taken asa sample of one or more substances that may be found in sweat.

The sweat sample may comprise a material selected from one of more of: anon-aqueous component of sweat, one or more organic compounds that maybe found in sweat, one or more ionic compounds that may be found insweat, and water.

The sweat sample may comprise a material selected from one or more of:ascorbic acid, thiamine, riboflavin, nicotinic acid, an amino acid,ethanol, antipyrine, creatinine, thiourea, lactate, theophylline,parathion, tetrahydrocannabinol, insulin, cimetidine, dimethylacetamide,fluorine, bromine, iron, bismuth, lactic acid, pyruvate glucose,ammonia, uric acid, nicotine, morphine, sulfanimide, atabrin, methadone,phencyclidine, aminopyrine, sulfadiacine, an amphetamine,benoylecgonine, phenobarbital, an androgen steroid, phenytoin, andcarbamazepine.

The or at least one of the storage means may comprise a storage sampleof porous silicon. The storage sample of porous silicon may have astructure and composition such that, when the storage sample of poroussilicon is brought into contact with simulated human sweat for a periodgreater than 10 minutes a sweat element is detectable by secondary ionmass spectrometry, in or on at least part of the storage sample ofporous silicon.

The or at least one of the storage means may comprise a storage sampleof porous silicon that has been partially oxidized, the partiallyoxidized porous silicon having a structure and composition such that,when the storage sample of porous silicon is brought into contact withsimulated human sweat for a period between 10 minutes and 48 hours, asweat element is detectable by secondary ion mass spectrometry, in or onat least part of the partially oxidized sample of porous silicon.

The or at least one of the storage means may comprise a storage sampleof porous silicon that has been partially oxidized, the partiallyoxidized porous silicon having a structure and composition such that,when the storage sample of porous silicon is brought into contact withhuman sweat for a period between 10 minutes and 48 hours, a sweatelement is detectable by secondary ion mass spectrometry, in or on atleast part of the partially oxidized sample of porous silicon.

For the purposes of this specification a sweat element is an elementthat may be found in sweat. The sweat element may be one or more ofsodium, chlorine, potassium, calcium, magnesium, lead, cadmium, zinc,and lithium. The sweat element or elements may form part of a compoundfound in sweat.

The storage sample of porous silicon may have a structure andcomposition such that, when the porous silicon is brought into contactwith a simulated human sweat for period greater than or equal to 10minutes, a sweat element is detectable by secondary ion massspectrometry, in or on at least part of the storage sample of poroussilicon.

The storage sample of porous silicon may have a structure andcomposition such that, when the storage sample of porous silicon isbrought into contact with simulated human sweat for a period greaterthan 10 minutes a sweat organic compound is detectable in or on at leastpart of the storage sample of porous silicon by a matrix assisted laserdesorption ionisation (MALDI) technique.

The value of the MALDI technique in relation to the detection ofbiomolecules that are present on a sample of porous silicon is describedin Nature Vol 399, p243-246 (1999).

The storage sample of porous silicon may be partially oxidized, thepartially oxidized porous silicon having a structure and compositionsuch that, when the partially oxidized porous silicon is brought intocontact with simulated human sweat for a period between 5 minutes and 6months, a sweat organic compound is detectable in or on at least part ofthe partially oxidized porous silicon by a matrix assisted laserdesorption ionisation (MALDI) technique.

The storage sample of porous silicon may be partially oxidized, thepartially oxidized porous silicon having a structure and compositionsuch that, when the partially oxidized porous silicon is brought intocontact with human sweat for a period between 5 minutes and 6 months, asweat organic compound is detectable in or on at least part of thepartially oxidized porous silicon by a matrix assisted laser desorptionionisation (MALDI) technique.

For the purposes of this specification, a sweat compound is a compoundthat may be found in sweat. A sweat compound may be a protein that maybe found in sweat.

The use of a storage means comprising porous silicon may be advantageoussince the porous silicon may perform a dual function of filtration andstorage. The porous silicon in the region of the skin acting as a filterby, for example, preventing entry of skin cells into the part of theporous silicon to be analyzed, but allowing passage of the sweat sample.Porous silicon also opens the way for the use of biasing to assist withdeposition of the body fluid sample on the storage means. It also allowsthe use of biasing to assist with the separation of the sweat sampleprior to analysis of the sample.

The attachable fluid collection device may comprise a semi-permeablemembrane. The semipermeable membrane may have a structure andcomposition such that it allows the passage, of at least one substancefound in sweat, through the membrane. The semipermeable membrane maycomprise porous silicon. The semipermeable membrane may comprisederivatized porous silicon. The semipermeable membrane may compriseporous silicon that has been partially oxidized. The or at least one ofthe storage means may be arranged such that it is in contact with thesemipermeable membrane. The or at least one of the storage means and thesemipermeable membrane may both be arranged such that they are incommunication with each other, so that a sweat sample may pass from thesemipermeable membrane to the or at least one of the storage means.

For the purposes of this specification, the term “derivatized poroussilicon” should be taken as porous silicon having a covalently boundmonolayer that has been formed on at least part of its surface. Examplesof derivatized porous silicon, falling within this definition, are givenin PCT/US99/01428.

The semipermeable membrane may comprise partially oxidized silicon. Thesemipermeable membrane may comprise partially oxidized porous silicon.

The storage sample of porous silicon and semipermeable membrane may bothform part of a unitary sample of porous silicon. The storage sample ofporous silicon and semipermeable membrane may both form part of aunitary sample of porous silicon that has been partially oxidized.

The unitary sample of porous silicon may have a low porosity small poresize layer, from which the semipermeable membrane is formed, connectedto a high porosity layer, from which the storage sample is formed. Theunitary sample of porous silicon may have a low porosity small pore sizelayer that has been partially oxidized, from which the semipermeablemembrane is formed, connected to a high porosity layer that has beenpartially oxidized, from which the storage sample is formed.

The unitary sample of porous silicon may have a low porosity from whichthe semipermeable membrane is formed, connected to a high porositylayer, from which the storage sample is formed. The unitary sample ofporous silicon may have a low porosity layer that has been partiallyoxidized, from which the semipermeable membrane is formed, connected toa high porosity layer that has been partially oxidized, from which thestorage sample is formed.

The fluid collection means may comprise derivatized porous silicon. Thederivatized porous silicon may comprise an organic compound, saidorganic compound comprising a carbon chain. For the purposes of thisspecification, derivatized porous silicon is to be taken as a type ofporous silicon.

Derivatization may be selected to allow wetting of the or at least oneof the storage means. Alternatively derivatization may be selected toenhance stability of the porous silicon against dissolution or corrosionby the body fluid. The derivatization may be such that the poroussilicon selectively binds to one component, or a limited number ofcomponents, in the body fluid.

Preferably the silicon, from which the or at least one of the storagemeans is at least partly formed, comprises derivatized porous silicon.More preferably the derivatized porous silicon has a structure such thatthe derivatized porous silicon is substantially un-corroded aftercontact with simulated human sweat for a period greater than or equal to10 minutes. Yet more preferably the derivatized porous silicon has astructure such that the derivatized porous silicon is substantiallyun-corroded after contact with simulated human sweat for a periodgreater than or equal to 1 day. Even more preferably the derivatizedporous silicon has a structure such that the derivatized porous siliconis substantially un-corroded after contact with simulated human sweatfor a period greater than or equal to 1 week.

The attachable collection device may further comprise a backing layer.The backing layer may be constructed in such a manner that it forms areceptacle for the or at least one of the storage means. At least partof the backing layer may form at least part of said attachment means.The backing member may be permeable or impermeable.

The backing layer may comprise silicon, the backing layer may comprisebulk crystalline silicon.

The backing layer may serve to isolate the collection means from theenvironment surrounding the attachable collection device, includingneighbouring areas of skin. The backing layer may be permeable to allowwater vapour to escape from the attachable collection device.

The ability of the storage sample of porous silicon to interact with, orgenerate, electromagnetic radiation, may be affected by contact with thesweat sample. Changes in such properties of porous silicon may be usedto detect the presence of, or analyze elements and compounds found insweat.

The or at least one of the storage means may comprise a storage sampleof porous silicon having a structure and composition such that contactbetween the porous silicon and at least part of the sweat sample causesa change in one or more of: the photoluminescence efficiency,photoluminescence spectrum, the reflectivity, the absorbance, and thephotoluminescence decay time of the porous silicon.

The or at least one of the storage means may comprise a storage sampleof porous silicon, which has been partially oxidized, the partiallyoxidized porous silicon having a structure and composition such thatcontact between the partially oxidized porous silicon and at least partof the sweat sample causes a change in one or more of: thephotoluminescence efficiency, photoluminescence spectrum, thereflectivity, the absorbance, and the photoluminescence decay time ofthe partially oxidized porous silicon.

The body fluid collection device may comprise at least one referencestorage means and at least one derivatized storage means. The or eachreference storage means comprising silicon. The or each derivatizedstorage means comprising derivatized silicon, the derivatization beingselected such that, when brought into contact with sweat, thederivatized silicon binds to a sweat element or sweat compound or partof a sweat compound. Preferably the derivatization is such that thederivatized porous silicon may bond covalently with a sweat element orpart of a compound when brought into contact with sweat containing saidelement or compound.

The use of reference and derivatized storage means may be advantageous.Analysis of both the reference and derivatized storage means may allowcomparison of the two types of storage means to determine whetherbinding to the sweat element or compound has occurred.

The body fluid collection device may comprise an electronic circuit. Thebody fluid collection means may comprise a means for determining theconductivity of the sweat sample. The body fluid collection device maycomprise a means for monitoring the electrical impedance of at leastpart of the silicon from which the or at least one of the storage meansis formed. The body fluid collection device may comprise a biasingmeans, for applying a potential difference across at least part of thesilicon from which the or at least one of the storage means is formed,and a means for measuring the current density resulting from saidpotential difference.

The body fluid collection means may comprise at least one first storagemeans and at least one second storage means. The or at least one of saidfirst storage means may comprise a first type of derivatized silicon,which is derivatized in such a manner that, when brought into contactwith sweat, the first type of derivatized silicon binds to a first sweatelement or compound. The or at least one of said second storage meansmay comprise a second type of derivatized silicon, which is derivatizedin such a manner that, when brought into contact with sweat, the secondtype of derivatized silicon binds to a second sweat element or compound.

The use of two types of derivatization allows the detection of more thanone element or compound found in sweat. A medical condition or presenceof drug in a subject may be indicated by the presence of more than oneelement or compound in the sweat of the subject. Measurement of therelative concentrations of the elements or compounds in the sweat mayalso provide useful information.

According to a second aspect, the invention provides a method ofcollecting a body fluid sample from an animal or human comprising thesteps:

(i) placing a silicon sample in fluid communication with part of a bodyfluid secreting surface of the animal or human;

(ii) allowing or causing the animal or human to express the body fluidsample; and

(iii) collecting the body fluid sample on or in at least part of thesilicon sample.

The method of collecting a body fluid sample may be a method ofcollecting and analyzing a body fluid sample, wherein the method furthercomprises the step (iv) of analyzing the body fluid sample that has beencollected on or in at least part of the silicon sample.

The step (i) may comprise the step of placing a silicon sample that hasbeen partially oxidized in fluid communication with part of a body fluidsecreting surface of the animal or human, and the step (iii) maycomprise the step of collecting the body fluid sample on or in at leastpart of the silicon sample that has been partially oxidized.

Preferably the body fluid sample is a sweat sample and step (i)comprises the step of (a) placing a silicon sample in fluidcommunication with part of the skin of the animal or human; step (ii)comprises the step of (b) allowing or causing the animal or person toexpress the sweat sample by sweating; step (iii) comprises the step of(c) collecting the sweat sample on or in at least part of the siliconsample.

The step (iv) of analyzing the body fluid sample may comprise the step(d) of analyzing the sweat sample that has been collected on or in atleast part of the silicon sample.

The step of (iv) of analyzing the body fluid sample may comprise thestep of detecting a body fluid sample, that has been collected on or inat least part of the silicon sample, by one of the following techniques:MALDI, SIMS, measurement of photoluminescence efficiency, measurement ofphotoluminescence spectra, reflectivity spectroscopy, absorbancespectroscopy, and measurement of photoluminescence decay time.

The step of analyzing the sweat sample may be performed after step (c)or it may be performed during at least part of step (c).

The step of analyzing the sweat sample may be performed while the sweatsample is in contact with at least part of the silicon sample.

The method may further comprise the step, which may be performed afterstep (c) and before the analysis step (d), of separating the sweatsample from the silicon sample.

The silicon sample may comprise one or more of: porous silicon,polycrystalline silicon, amorphous silicon, bulk crystalline silicon,bioactive silicon, resorbable silicon, biocompatible silicon, andderivatized porous silicon.

The silicon sample may comprise porous silicon that has been partiallyoxidized.

Preferably the silicon sample comprises a storage sample of derivatizedporous silicon and step (c) comprises the step of collecting the sweatsample over a period of less than or equal to than 10 minutes, andallowing the storage sample of derivatized porous silicon to besubstantially uncorroded during the collection period. Preferably thesilicon sample comprises a storage sample of derivatized porous siliconand step (c) comprises the step of collecting the sweat sample over aperiod of less than or equal to than 20 hours, and allowing the storagesample of derivatized porous silicon to be substantially uncorrodedduring the collection period. Preferably the silicon sample comprises astorage sample of derivatized porous silicon and step (c) comprises thestep of collecting the sweat sample over a period of less than or equalto than 1 week, and allowing the storage sample of derivatized poroussilicon to be substantially uncorroded during the collection period.

Preferably the silicon sample comprises a storage sample of poroussilicon and step (c) comprises the step of collecting the sweat sampleover a period of less than or equal to than 10 minutes, and allowing thestorage sample of porous silicon to be substantially uncorroded duringthe collection period. Preferably the silicon sample comprises a storagesample of porous silicon and step (c) comprises the step of collectingthe sweat sample over a period of less than or equal to than 20 hours,and allowing the storage sample of porous silicon to be substantiallyuncorroded during the collection period. Preferably the silicon samplecomprises a storage sample of porous silicon and step (c) comprises thestep of collecting the sweat sample over a period of less than or equalto than 1 week, and allowing the storage sample of porous silicon to besubstantially uncorroded during the collection period.

Step (a) may comprise the step of bringing a storage sample of poroussilicon into contact with the skin of a human or animal for a period ofgreater than or equal to 10 minutes so that a sweat element is collectedin or on at least part of the storage sample of porous silicon, and step(c) may comprise the step of detecting the sweat element, which has beendeposited on at least part of the sample of porous silicon, by secondaryion mass spectrometry.

Step (a) may comprise the step of bringing a storage sample of poroussilicon into contact with a sweat sample for a period of greater then orequal to 10 minutes so that a sweat organic molecule is collected in oron at least part of the storage sample of porous silicon, and step (c)may comprise the step of detecting the sweat organic molecule, that hasbeen deposited on at least part of the sample of porous silicon, by aMALDI technique.

Step (a) may comprise the step of bringing a storage sample of poroussilicon into contact with a sweat sample, and step of analyzing thesweat sample may comprise the step of monitoring a change in one or moreof: the photoluminescence efficiency, photoluminescence spectrum, thereflectivity, the absorbance, and the photoluminescence decay time of atleast part of the storage sample of porous silicon, said changeresulting from the contact with the sweat sample.

The step (c) may comprise the step of applying a bias to the siliconsample in such a manner that the rate of collection of the sweat sampleis accelerated, relative to the rate of deposition when the siliconsample is at earth potential. The step (c) may comprise the step ofapplying a bias to the porous silicon in such a manner that the rate ofdeposition of the sweat sample on the silicon is accelerated, relativeto the rate of deposition when the silicon sample is at earth potential.

The step of separating the sweat sample from the silicon sample, priorto the analysis step, may comprise the step of immersing at least partof the silicon sample in a solvent. The step of separating the sweatsample from the silicon sample, when it is at least partly immersed inthe solvent, may further comprise the step of applying a bias to thesilicon sample in such a manner that the bias increases the rate atwhich the sweat sample moves from the silicon sample into the solvent,relative to the rate when the silicon sample is at earth potential.

The solvent may comprise one or more of water, ethanol, and acetone. Thesolvent may comprise any organic compound that is a liquid at 20 C. anda pressure of 760 mm Hg.

According to a third aspect the invention provides a use of a sample ofsilicon in the preparation of a medicament for collecting and analyzing,or for collecting and subsequently releasing for analysis, a body fluidsample from an animal or human.

The term “medicament” as used herein refers to any substance used intherapy or diagnosis.

The body fluid sample may be a sweat sample. Preferably the step ofcollecting the body fluid sample from the animal or human comprises thestep of collecting a sweat sample from part of the skin of an animal orhuman.

The step of analyzing may comprise the step of detecting a sweat sample,that has been collected on or in at least part of the sample of silicon,by one of the following techniques: MALDI, SIMS, measurement ofphotoluminescence efficiency, measurement of photoluminescence spectra,reflectivity spectroscopy, absorbance spectroscopy, and measurement ofphotoluminescence decay time.

The step of releasing for analysis may comprise the step of releasing asweat sample, that has been collected on or in at least part of thesample of silicon, for detection by one of the following techniques:MALDI, SIMS, photoluminescence spectroscopy, reflectivity spectroscopy,absorbance spectroscopy, and fluorescence spectroscopy.

The step of releasing for analysis may comprise the step of at leastpartly immersing the sample of silicon in a solvent so that the bodyfluid sample passes from the sample of silicon into the solvent.

The step of collecting the body fluid sample may comprise the step ofincreasing the rate of collection, relative to the rate of collectionwhen the sample of silicon is at earth potential, by applying a bias tothe sample of silicon.

The step of releasing the sample for analysis may comprise the step ofincreasing the rate of release, relative to the rate of release when thesample of silicon is at earth potential, by applying a bias to thesample of silicon.

The sample of silicon may comprise one or more of: porous silicon,polycrystalline silicon, amorphous silicon, bulk crystalline silicon,bioactive silicon, resorbable silicon, biocompatible silicon, andderivatized porous silicon.

The sample of silicon may comprise partially oxidized silicon. Thesample of silicon may comprise partially oxidized porous silicon.

Preferably the sample of silicon comprises a storage sample of poroussilicon and step of collecting the body fluid sample comprises the stepof collecting a sweat sample over a period of less than or equal to than10 minutes, and allowing the storage sample of porous silicon to besubstantially uncorroded during the collection period. Preferably thesample of silicon comprises a storage sample of porous silicon and stepof collecting the body fluid sample comprises the step of collecting asweat sample over a period of less than or equal to than 20 hours, andallowing the storage sample of porous silicon to be substantiallyuncorroded during the collection period. Preferably the sample ofsilicon comprises a storage sample of porous silicon and step ofcollecting the body fluid sample comprises the step of collecting asweat sample over a period of less than or equal to than 1 week, andallowing the storage sample of porous silicon to be substantiallyuncorroded during the collection period.

Advantageously the sample of silicon comprises a storage sample ofpartially oxidized porous silicon and step of collecting the body fluidsample comprises the step of collecting a sweat sample over a period ofless than or equal to than 10 minutes, and allowing the storage sampleof partially oxidized porous silicon to be substantially uncorrodedduring the collection period. Preferably the sample of silicon comprisesa storage sample of partially oxidized porous silicon and step ofcollecting the body fluid sample comprises the step of collecting asweat sample over a period of less than or equal to than 20 hours, andallowing the storage sample of partially oxidized porous silicon to besubstantially uncorroded during the collection period. Preferably thesample of silicon comprises a storage sample of partially oxidizedporous silicon and step of collecting the body fluid sample comprisesthe step of collecting a sweat sample over a period of less than orequal to than 1 week, and allowing the storage sample of partiallyoxidized porous silicon to be substantially uncorroded during thecollection period.

The sweat sample may comprise a material selected from one of more of: anon-aqueous component of sweat, one or more organic compounds that maybe found in sweat, one or more ionic compounds that may be found insweat, and water.

The sweat sample may comprise a material selected from one or more of:ascorbic acid, thiamine, riboflavin, nicotinic acid, an amino acid,ethanol, antipyrine, creatinine, thiourea, lactate, theophylline,parathion, tetrahydrocannabinol, insulin, cimetidine, dimethylacetamide,fluorine, bromine, iron, bismuth, lactic acid, pyruvate glucose,ammonia, uric acid, nicotine, morphine, sulfanimide, atabrin, methadone,phencyclidine, aminopyrine, sulfadiacine, an amphetamine,benoylecgonine, phenobarbital, an androgen steroid, phenytoin, andcarbamazepine.

According to a fourth aspect, the invention provides an attachable bodyfluid collection device comprising at least one storage means for, whenin use, storing a body fluid sample secreted by a body fluid secretingsurface, characterised in that the or at least one of the storage meanscomprises silicon oxide.

Preferably the silicon oxide has the chemical formula SiOx where0.1≦x≦2.

Advantageously the silicon oxide is porous silicon oxide, moreadvantageously the porous silicon oxide is integral with a substrate.The substrate may comprise one or more of: bulk crystalline silicon,silicon oxide, or partially oxidized bulk crystalline silicon.

According to a fifth aspect, the invention provides a method ofcollecting a body fluid sample from an animal or human comprising thesteps:

(i) placing a silicon oxide sample in fluid communication with part of abody fluid secreting surface of the animal or human;

(ii) allowing or causing the animal or human to express the body fluidsample; and

(iii) collecting the body fluid sample on or in at least part of thesilicon oxide sample.

Advantageously the silicon oxide is porous silicon oxide, moreadvantageously the porous silicon oxide is integral with a substrate.The substrate may comprise one or more of: bulk crystalline silicon,silicon oxide, or partially oxidized bulk crystalline silicon.

According to a sixth aspect the invention provides a use of a sample ofsilicon oxide in the preparation of a medicament for collecting andanalyzing, or for collecting and subsequently releasing for analysis, abody fluid sample from an animal or human.

Advantageously the silicon oxide is porous silicon oxide, moreadvantageously the porous silicon oxide is integral with a substrate.The substrate may comprise one or more of: bulk crystalline silicon,silicon oxide, or partially oxidized bulk crystalline silicon.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only withreference to the following drawings, in which:

FIG. 1 is a schematic diagram of a prior art sweat patch;

FIG. 2 a is a schematic diagram of an attachable body fluid collectiondevice according to the invention;

FIG. 2 b is a schematic diagram of a storage sample of porous siliconthat may form part of a body fluid collection device according to theinvention;

FIG. 3 shows SIMS depth profiles for a number of sweat elements, theSIMS measurements being performed on the porous silicon samplerepresented in FIG. 2 b, prior to contact with sweat;

FIG. 4 shows SIMS depth profiles for a further group of sweat elements,the SIMS measurements being performed on the FIG. 2 b porous siliconsample, prior to contact with sweat;

FIG. 5 shows a schematic diagram of a body fluid collection device,according to the invention, comprising three body fluid storage means;

FIG. 6 shows a schematic diagram of a body fluid collection device,according to the invention, comprising a means for monitoring theresistance of a storage sample of porous silicon;

FIG. 7 shows SEM images of a third storage sample of porous silicon thathas been partially oxidized and for a fourth storage sample of poroussilicon that is un-oxidized, the images shows the effect of immersion insimulated sweat for these two samples of porous silicon;

FIG. 8 shows a SIMS profile for a second storage sample of poroussilicon, the image shows the effect of immersion in simulated sweatcontaining lithium ions;

FIG. 9 shows an apparatus to determine the behaviour of a storage sampleof porous silicon, under an electrical bias, in simulated human sweat;

FIG. 10 shows a SIMS profile for a second storage sample of poroussilicon and to which an anodic electric bias has been applied, the imageshows the effect of immersion in simulated sweat containing lithiumions;

FIG. 11 shows a SIMS profile for a second storage sample of poroussilicon and to which an cathodic electric bias has been applied, theimage shows the effect of immersion in simulated sweat containinglithium ions;

FIG. 12 shows a SIMS profile for a fifth storage sample of poroussilicon that has been partially oxidized, the image shows the effect ofimmersion in simulated sweat containing lithium ions;

FIG. 13 shows a SIMS profile for a fifth storage sample of poroussilicon that has been partially oxidized, the image shows the effect ofimmersion in simulated sweat containing lithium ions; and

FIG. 14 shows a SIMS profile for a fifth storage sample of poroussilicon that has been partially oxidized, the image shows the effect ofcontact with human skin.

DESCRIPTION OF PREFERRED EMBODIMENTS Structure, Composition, andFabrication

FIG. 2 a shows a schematic diagram of an attachable body fluidcollection device, generally indicated by 21, according to theinvention. The fluid collection device 21 comprises a storage means 22,and an attachment means 23. The storage means comprises a first storagesample of porous silicon 24, and a portion of bulk crystalline silicon25. The first storage sample of porous silicon 24 may comprisederivatized porous silicon.

The first storage sample of porous silicon may be prepared by a method,which will be referred to as “method A”, which comprises the step ofanodising bulk crystalline silicon by a standard technique such as thatdescribed in U.S. Pat. No. 5,348,618. The resulting first storage sampleof porous silicon 24 is connected to the remaining portion of bulkcrystalline silicon 25. The attachment means 23 holds the storage meansin contact with a body fluid secreting surface, which in this case ishuman skin 26. The attachment means 23 may, for example, be an adhesivetape, the adhesive being present on only one side of the tape.

Any reference, in this specification, to a “first storage sample ofporous silicon” should be taken as a reference to a storage sample ofporous silicon prepared by method A.

FIG. 2 b shows a schematic diagram of a second storage sample of poroussilicon 224 a. The second storage sample of porous silicon wasfabricated by the following method, which will be referred to as “methodB”:

A 0.005 ohm cm p+ wafer was anodised in 20% ethanoic HF. A currentdensity of 5 mA cm⁻² was passed for 120 seconds, immediately followed bya current density of 50 mA cm⁻² for 120 seconds.

The application of two consecutive current densities in this waygenerated two layers 224 a, 224 b of porous silicon, one having a highporosity 224 a, which forms the second storage sample of porous silicon224 a, and the other having low porosity 224 b, which forms asemipermeable membrane. The low and high porosity layers 224 a and 224 bare connected to each other. The porosity of the second storage sampleof porous silicon 224 a, which is connected to the bulk crystallinesubstrate 224 c, is 67%. The porosity of the semipermeable membrane 224b is 43%.

A storage sample of porous silicon prepared by method B will be referredto, in this specification, as a “second storage sample of poroussilicon”.

The low porosity semipermeable membrane 224 b could be used to preventdermal detritus reaching the higher porosity second storage sample ofporous silicon 224 a used to store the sweat sample.

FIG. 3 shows the SIMS depth profiles for the sweat elements: sodium,potassium, and lithium in the second storage sample of porous silicon,prior to exposure to sweat. Trace sodium is present throughout the layerat parts per million levels, this is indicated by the abrupt change inlevel with sputtering time as the sputtered region passes from theporous layer 224 a into the underlying bulk crystalline substrate 224 c.The results for sodium contrast with those for potassium and lithium,which are at the limits of detection by this technique, no correspondingchange in signal level between the porous and bulk regions beingobserved for these two elements.

FIG. 4 shows SIMS depth profiles for three sweat elements: iron, lead,and copper in the second storage sample of porous silicon 224 a prior toexposure to sweat. Copper is detectable at levels of the order of partsper million, whilst iron and lead are undetectable.

FIGS. 3 and 4 both show a SIMS depth profile for silicon. The variationof the SIMS signal with sputtering time provides an indication of theboundaries of the porous silicon layers. The signal resulting fromsilicon is present in all of the SIMS results presented in this patentapplication.

A Body Fluid Collection Device Comprising Three Storage Means

FIG. 5 shows a schematic diagram of a body fluid collection device,generally indicated by 51, according to the invention. The collectiondevice 51 comprises a type x storage means 52, a type y storage means53, and a type z storage means 54. Each storage means comprises poroussilicon. The three storage means are in contact with the surface of theskin 55 of a subject. The storage means are attached by means of anattachment means 66 having adhesive surfaces 57 and 58. The type xstorage means 52 may comprise type x derivatized porous silicon, thetype y storage means 53 may comprise type y derivatized porous silicon,and the type z storage means 54 may comprise type z derivatized poroussilicon. Each type of derivatization may be selected so that when thethree storage means are brought into contact with the skin surface, andconditions are such that sweating occurs, the storage means eachselectively bind to a different component of the sweat. In this waydifferent sweat elements and compounds can be collected simultaneously.

In an alternative embodiment multiple storage means may be formed on asingle silicon substrate. Each storage sample may comprise a differenttype of derivatized porous silicon that selectively binds to a differentsweat component. The silicon substrate may comprise bulk crystallinesilicon.

Measurement of the Chance in Conductivity of a Storage Sample of PorousSilicon as a Result of the Presence of Sweat

FIG. 6 shows a schematic diagram of a body fluid collection device,generally indicated by 61, according to the invention. The body fluidcollection device 61 comprises a first storage sample of porous silicon62, and attachment means 63, two electrodes 63, 64, a biasing means 65,and an ammeter 66. The first storage sample of porous silicon 62 isattached to the surface of the skin 67 of a subject 67 by the attachmentmeans 63. The subject is made or allowed to sweat while the body fluidcollection device is in contact with the skin, and the resulting changein the conductivity is monitored by means of the ammeter.

The Effect of Partial Oxidation on the Stability of a Storage Sample ofPorous Silicon in Simulated Human Sweat

A third storage sample of porous silicon was prepared by the followingmethod, which will be referred to as “method C”:

A 0.005 ohm cm wafer was anodised in 20% ethanoic HF at 5 mA cm⁻² for120 seconds and then 50 mA cm⁻² for 10 minutes. Half of the anodisedwater was then partially oxidied by thermal treatment in air at 500 C.for 30 minutes to yield the third storage sample of porous silicon.

Any sample referred to, in this specification, as a “third storagesample of porous silicon”, should be taken as a sample of porous siliconprepared by method C.

A fourth storage sample of porous silicon was prepared by the followingmethod, which will be referred to as “method D”:

The half of the anodised wafer that was not oxidised in method B, wasstored in air at room temperature for a period of 12 days to yield thefourth sample of porous silicon.

Any sample referred to, in this specification, as a “fourth sample ofporous silicon” should be taken as a sample of porous prepared by methodD.

Segments of the third and fourth storage samples of porous silicon werethen incubated in simulated human sweat at 25 C. The simulated humansweat was prepared in accordance with ISO standard (3160/2) and isdescribed by J P Randin in J. Biomed. Mater. Res. 22, 649 (1988). Thesimulated human sweat comprises NaCl (20 g/litre), NH4Cl (17.5 g/litre),urea (5 g/litre), acetic acid (2.5 g/litre), and lactic acid (15g/litre). The pH of the simulated human sweat was adjusted to 6.5 byaddition of NaOH.

FIG. 7(a) is a cross-sectional SEM image of the third storage sample ofporous silicon. FIG. 7(b) shows a higher magnification image of the samesample, the image being of the lower porosity region close to thesurface of the sample. FIG. 7(c) shows the third storage sample ofporous silicon after 9 days immersion in simulated sweat. There issubstantially no corrosion resulting from this period of immersion.

FIG. 7(d) shows the fourth storage sample of porous silicon, after 9days immersion in simulated sweat. As can be seen from the SEM image,significant corrosion has occurred.

The Effect of Applying an Electrical Bias to the Storage Properties of aStorage Sample of Porous Silicon

FIG. 8 shows a SIMS profile for a second storage sample of poroussilicon after 40 minutes immersion in simulated human sweat to which alithium ions have been added to make the concentration of lithium ionsin the simulated human sweat equal to 2 millimolar. The lithium ionswere added in the form of lithium nitrate. A comparsion of the sodiumand lithium profiles of FIG. 8 with those of FIG. 3 shows that thesimulated sweat has substantially not entered the high porosity porouslayer 81.

FIG. 9 shows a storage means 91 that has been partly immersed insimulated human sweat 92. The storage means comprises a first storagesample of porous silicon 93, and a portion of bulk cystalline silicon54, the porous silicon 93 being in contact with the bulk crystallinesilicon 54. The first storage sample of porous silicon 93 may comprisederivatized porous silicon. An electrode 95 is attached to the portionof bulk crystalline silicon and maintained at a constant potentialrelative to earth by means of a power supply 96. The simulated humansweat 92 comprises an aqueous solution of NaCl (20 g/litre), NH4Cl (17.5g/litre), urea (5 g/litre), acetic acid (2.5 g/litre), and lactic acid(15 g/litre). The pH of the solution was adjusted to 5.5 by the additionof NaOH. This corresponds to ISO standard (3160/2), which is describedby J P Randin in J Biomed Mater Res 22, 649 (1988). Experiments wereperformed at potentials between 0V and +−50 V over periods of immersionbetween 10 minutes and 1 week.

After the period of immersion is complete the first storage sample ofporous silicon 93 is removed from the simulated human sweat 92 andsubjected one or more of the following analytical techniques: MALDI,SIMS, and SEM. The sample may also be analyzed by one of:photoluminsecence spectroscopy, relectivity spectroscopy, absorancespectroscopy, and fluorescence spectroscopy. MALDI may be used todetermine the uptake of organic sweat molecules, SIMS may be used todetermine the uptake of sweat elements, SEM may be used to determine thecorrosion or absence of corrosion by the simulated human sweat. Thespectroscopic analysis may be used to determine the presence of a sweatsample on or in the first storage sample of porous silicon 93.

FIG. 10 also shows a SIMS depth profile for a second storage sample ofporous silicon, to which an anodic bias has been applied (2 mA cm⁻² at1.5 V for 10 minutes). The profile was obtained after immersion, at theanodic potential, for 10 minutes in simulated human sweat to which alithium ions, in the form of lithium nitrate. The lithium ions arepresent in the simulated human sweat at a concentration of 2 millimolar.The FIG. 10 results are markly different from those of FIG. 9. Thesodium level throughout the high porosity layer 81 has risen by threeorders of magnitude, and the lithium concentration in the high porositylayer has risen by more than three orders of magnitude. By contrast theorganic components of the simulated sweat have been impeded by the lowporosity layer 82.

FIG. 11 shows the SIMS depth profiles for the second storage sample ofporous silicon, after a cathodic electrical bias (2 mA cm⁻² at 3.0 V)has been applied to the sample for 10 minutes. The cathodic bias wasalso found to promote wetting, but with more diffusion like propertiesover these short time scales.

The Effect of Partial Oxidation on the Wettability of a Storage Sampleof Porous Silicon

A fifth storage sample of porous silicon was prepared by the followingmethod, which will be referred to as “method E”:

A second storage sample was partially oxidized in air at 500 C. for 30minutes to yield the fifth sample of porous silicon.

References in this specification to a “fifth storage sample of poroussilicon” should by taken as reference to a storage sample of poroussilicon prepared by method E.

The fifth storage sample of porous silicon was incubated in simulatedhuman sweat containing lithium ions (the concentration of lithium ionsin the simulated human sweat being equal to 2 m mol/litre) for 40minutes. FIG. 12 show a SIMS plot for a fifth storage sample of poroussilicon after this immersion in simulated sweat. The FIG. 12 resultsshow improved wetting by cations, relative to the second storage sampleof porous silicon, without any application of an electrical bias. TheFIG. 12 sodium and lithium profiles are very similar, in terms of shapeof the profile, to those shown in FIG. 10. The result shows that partialoxidation of a sample of porous silicon may improve wetting of thesample by cations present in simulated human sweat.

Relationship Between SIMS Measurements and Concentration of a SweatElement

A fifth storage sample of porous silicon was immersed in simulatedhuman, containing lithium ions, sweat for 10 minutes. The concentrationof lithium ions in the simulated human sweat solution was 0.2 mmol/litre, which is ten times lower than for the simulated human sweatused to obtain the FIG. 12 results. The SIMS results for the lowerlithium concentration are shown in FIG. 13.

A comparsion of the FIG. 12 and FIG. 13 results shows that theconcentration of lithium present in the fifth storage sample of poroussilicon is approximately ten times lower in the FIG. 13 sample than inthe FIG. 12 sample. In other words the FIGS. 12 and 13 results show thatthere is an approximately linear relationship between concentration oflithium in the simulated sweat solution and the concentration in thestorage sample of porous silicon.

FIG. 13 also shows that lithium signal corresponding to the 0.2 mmol/litre concentration is approximately 200 times the backgroundsignal. This result, combined with the approximate linearity between thelithium concentration in simulated sweat, and the SIMS signal from thestorage sample of porous silicon, suggests that lithium concentrationsas low as 1 micro mol/litre might be detectable. Indeed, if lithiumconcentrations were to accumulate over time, concentrations much lowerthat this could be detected, by collecting the lithium over a periodgreater that the ten minute duration of the FIG. 13 experiment.

The Effect of Human Sweat on a Storage Sample of Porous Silicon

Once the first storage sample of porous silicon 24 has been in contactwith the skin of a human subject for a period of between 10 minutes and1 week, under conditions which cause the area of skin in contact withthe storage sample to sweat, it is removed from the skin and subjectedto one of the following analytical techniques: MALDI, SIMS, and SEM. Thesample may also be analyzed by one of: photoluminescence spectroscopy,reflectivity spectroscopy, absorance spectroscopy, and fluroescencespectroscopy. MALDI may be used to determine the uptake of organic sweatmolecules, SIMS may be used to determine the uptake of sweat elements,SEM may be used to determine the corresion or absence of corrosion bythe sweat. The spectoscopy analysis may be used to determine thepresence of a sweat sample on or in the storage sample of porous silicon24.

A fifth storage sample of porous silicon, having a length and width eachof 10 mm was attached to the front of a wrist of a human subject. Thestorage sample was attached to the wrist by an elastoplast for 40minutes, with its porous face in direct contact with the skin of thewrist. During this period the subject performed gentle exercise. FIG. 14shows the SIMS depth profiles for the prominent sweat components: Na, K,Ca, Mg, and C, together with the trace elements: Fe, Cu, Pb, and Li. Acomparsion of FIG. 14 with that of FIG. 12, shows that the level ofcarbon in the fifth storage sample of porous silicon, as a result ofattachment to a human subject, has risen by 100 times relative toexposure to simulated human sweat.

Measurement or Detection of a Sweat Sample After Separation from aStorage Sample of Porous Silicon

After the sweat sample has been collected on a storage sample of poroussilicon, it may be separated from the sample of porous silicon forexample by immersing the silicon in a solvent.

The sweat sample my then be measured or detected by one of the followingtechniques: high pressure liquid chromatograpy (HPLC), enzymen immunoassay (EIA), atomic absorption spectroscopy (AAS), anodic strippingvoltammetry (ASV), and gel electrophoresis (GE).

EIA may be used for peptides and is described in U.S. Pat. No.6,132,975, AAS may be used for trace metals and is described in ClinicaChimica Acta Vol 2312, P23-28 (1994), ASV may be used for trace metalsand is described in Sci Total Environ. Vol 60, p263-271 (1987), GE maybe used for proteins and is described in Analyt. Biochem. Vol 131,p520-524 (1983).

An alternative method by which the sweat sample may be combined with aliquid is by dissolving a porous silicon storage sample of poroussilicon, on or in which a sweat sample has been collected, by reactingthe porous silicon with a suitable alkali. For example porous siliconmay be dissolved by aqueous NaOH, and by aqueous KOH. The alkali aqueoussolution of the porous silicon and sweat sample, may then analyzed by anappropriate technique.

1. An attachable body fluid collection device comprising at least onestorage means for, when in use, storing a body fluid sample secreted bya body fluid secreting surface, the at least one storage meanscomprising porous silicon, porous silicon oxide, or a combination ofporous silicon and porous silicon oxide, wherein the collection devicefurther comprises means for applying a bias to at least part of thesilicon such that, when in use, the bias causes a rate of body fluidsample deposition on the storage means to be higher than that at groundpotential.
 2. A fluid collection device according to claim 1, whereinthe device further comprises attachment means for attaching the at leastone storage means to part of a surface of an animal or human body.
 3. Afluid collection device according to claim 1, wherein the device furthercomprises a backing layer, the backing layer having a structure andcomposition such that, when in use, it isolates the at least one storagemeans from environment surrounding the collection device.
 4. A fluidcollection device according to claim 1, wherein the silicon comprisesporous silicon oxide.
 5. A fluid collection device according to claim 4,wherein the silicon comprises partially oxidized porous silicon having astructure and composition such that it is substantially un-corrodedafter contact with human sweat for a period between 10 minutes and 10days.
 6. A fluid collection device according to claim 4, wherein thesilicon comprises partially oxidized porous silicon having a structureand composition such that it is substantially un-corroded after contactwith simulated human sweat for an interval of between 5 minutes and onemonth.
 7. A method of collecting a body fluid sample from an animal orhuman comprising: (i) placing a sample of porous silicon or poroussilicon oxide, or a combination thereof, in fluid communication withpart of a body fluid secreting surface of the animal or human; (ii)allowing or causing the animal or human to express the body fluidsample; and (iii) collecting the body fluid sample on or in at leastpart of the sample, wherein the collecting further comprises applying abias to the sample in such a manner that a rate of collection of thebody fluid sample is accelerated, relative to the rate of collection,when the sample is at ground potential.
 8. A method according to claim7, wherein the method further comprises analyzing the body fluid samplethat has been collected on or in at least part of the sample.
 9. Amethod according to claim 8, wherein the analyzing further comprisesdetecting a body fluid sample that has been collected on or in at leastpart of the sample, by one or more of the following techniques: MALDI,SIMS, measurement of photoluminescence efficiency, measurement ofphotoluminescence spectra, reflective spectroscopy, absorancespectroscopy, and measurement of photoluminescence decay time.
 10. Amethod according to claim 8, wherein the analyzing further comprisesanalyzing the body fluid sample that has been collected on at least partof the sample for a period between 1 hour and 24 hours.
 11. A methodaccording to claim 8, further comprising separating the body fluidsample from the sample prior to the analyzing, by bringing the at leastpart of the sample into contact with a solvent, so that at least part ofthe body fluid sample passes into the solvent.
 12. A method according toclaim 11, wherein the separating further comprises applying a bias tothe sample in such a manner that the bias increases the rate at whichthe sweat sample moves from the sample into the solvent, relative to therate when the sample is at ground potential.
 13. A method according toclaim 7, wherein (i) the placing comprises placing a sample in fluidcommunication with skin of an animal or human, (ii) the allowing orcausing comprises allowing or causing the animal or human to sweat; and(iii) the collecting comprises collecting a sample of sweat on or in atleast part of the sample.
 14. A method according to claim 7, wherein (i)the placing further comprises bringing the sample into contact with thefluid secreting surface.
 15. A method according to claim 7, wherein thesilicon comprises partially oxidized porous silicon, and (i) the placingcomprises placing the sample of partially oxidized porous silicon influid communication with part of the body fluid secreting surface.